http://www.irs.gov/publications/p505/ch04.html
No penalty. Generally, you will not have to pay a penalty for 2008 if any of the following situations apply.
* The total of your withholding and estimated tax payments was at least as much as your 2007 tax (or 110% of your 2007 tax if your adjusted gross income (AGI) was more than $150,000, $75,000 if your 2008 filing status is married filing separately), and you paid all required estimated tax payments on time.
* The tax balance due on your return is no more than 10% of your total 2008 tax, and you paid all required estimated tax payments on time.
* Your total 2008 tax (defined on page 55) minus your withholding is less than $1,000.
* You did not have a tax liability for 2007.
* You did not have any withholding taxes and your current year tax less any household employment taxes is less than $1,000.
